Small punch test device for testing hydrogen-induced performance damage of materials under hydrogen environment

Abstract

The application relates to the field of material testing, in particular to a small punch test device for testing hydrogen-induced performance damage of materials under a hydrogen environment, which comprises an upper clamp, a lower clamp, a positioning cylindrical shell and a punch; the upper clamp and the lower clamp are screw-connected, the positioning cylindrical shell is arranged in a cavity of the upper clamp, and the punch is arranged in the positioning cylindrical shell; the upper clamp comprises upper and lower series-connected upper and lower cylindrical shells, and the upper clamp comprises, from top to bottom, a first cavity, a second cavity and a third cavity in sequence; electrolyte and a platinum sheet electrode are arranged in the upper cylindrical shell, a sample groove and a sealing ring groove are arranged on the top surface of the third cavity, the positioning cylindrical shell is arranged in the third cavity of the upper clamp, the positioning cylindrical shell protrudes from the upper clamp after being arranged in the upper clamp, and a disc is arranged on the lower part of the punch. The small punch test device for testing hydrogen-induced performance damage of materials under a hydrogen environment is easy to manufacture, install, use and maintain, and can quickly evaluate the hydrogen-induced mechanical performance damage degree of materials.

Description

Technical Field

[0001] This invention belongs to the field of materials testing, specifically, it relates to a small punch test device for testing hydrogen-induced performance damage of materials in a hydrogen environment. Background Technology

[0002] Due to its unique physical and chemical properties, hydrogen can cause a certain degree of damage to pipe materials compared to other gases, thereby accelerating pipeline failure. Hydrogen embrittlement (HE), hydrogen-induced cracking (HIC), and fatigue in a hydrogen environment are the main destructive factors currently considered in pipeline construction. With the accelerated construction of hydrogen-blended and pure hydrogen pipelines in my country, it is sometimes necessary to test the hydrogen resistance of in-service pipelines without interrupting gas supply and transportation. This necessitates a minimally invasive or near-non-destructive evaluation of the hydrogen-induced performance damage to the steel and welded joints of hydrogen transport pipelines. Simultaneously, obtaining appropriately sized samples from in-service pipelines has become a critical issue. Many researchers use slow strain rate tensile tests to study the hydrogen embrittlement susceptibility of materials; however, traditional tensile test specimens are large, and sampling is destructive to the pipeline. Obtaining tensile test specimens from in-service pipelines is difficult, especially for weak points such as welded joints, where traditional tensile tests cannot provide effective assessment, necessitating alternative testing methods.

[0003] Small Punch Test (SPT) is a materials testing method that emerged in the 1980s. Initially used in the nuclear industry to assess radiation damage and high-temperature performance of nuclear reactor materials, its application has expanded to aerospace, oil and gas, and materials science research to evaluate material performance under extreme conditions such as high pressure and corrosion. One of SPT's advantages is its minimally invasive sampling. Samples are typically small circular pieces (10mm in diameter, 0.5mm thick) or small square pieces (10mm on each side, 0.5mm thick). This requires only a small amount of material to assess various mechanical properties under different environmental conditions, including tensile, compressive, fatigue, and fracture toughness. It is particularly suitable for rare, expensive, or difficult-to-prepare large-size materials, and also for evaluating the properties of small or localized areas, such as the mechanical properties of welds or coatings. The SPT process is relatively simple and quick, making it suitable for rapid screening and evaluation of material properties. To date, small punch testing technology has been widely used to test the conventional mechanical properties of materials. However, there is relatively little research on its application in in-situ testing of materials' hydrogen embrittlement sensitivity or resistance to hydrogen damage in hydrogen environments. One reason for this is the lack of in-situ testing devices suitable for small punch testing in hydrogen environments. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention proposes a small punch test device for testing hydrogen-induced mechanical property damage of materials in a hydrogen environment. It is easy to manufacture, install, use and maintain, and can quickly assess the degree of hydrogen-induced mechanical property damage of materials.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A small punch test apparatus for testing hydrogen-induced performance damage of materials under hydrogen environment includes: an upper clamp, a lower clamp, a positioning cylindrical shell, and a punch; the upper clamp and the lower clamp are fastened together, the positioning cylindrical shell is set in the cavity of the upper clamp, and the punch is set in the positioning cylindrical shell; wherein: the upper clamp includes an upper cylindrical shell and a lower cylindrical shell connected in series, and the upper clamp includes a first cavity, a second cavity, and a third cavity from top to bottom; the upper cylindrical shell is equipped with electrolyte and platinum sheet electrode, the top surface of the third cavity is provided with sample groove and sealing ring groove, the positioning cylindrical shell is set in the third cavity of the upper clamp and is clearance-fitted with the upper clamp, the positioning cylindrical shell protrudes from the upper clamp after being installed in the upper clamp, and a disk is set at the lower part of the punch, with a thin wall set around the disk.

[0006] Compared with the prior art, the beneficial effects of the present invention are as follows: Based on the small punch test device for testing the hydrogen-induced performance damage of materials under hydrogen environment, when it is necessary to test the hydrogen-induced damage resistance of materials, a fluororubber O-ring is placed in the sealing ring groove set in the third cavity of the upper clamp, and then the test sample is placed in the sample groove. The sample is a small circular piece with a diameter of 10mm and a thickness of 0.5mm. Then, the positioning cylindrical shell is placed into the third cavity, and the lower clamp and upper clamp are threaded together to ensure that the upper and lower clamps are tightened, ensuring that the sample can be stably fixed in the sample groove. After installation, an appropriate amount of water is added through the large hole set in the top of the upper clamp. After 5 minutes, the device is observed through the holes set in the lower clamp and the positioning cylindrical shell to check whether it has good sealing performance. If the sealing performance is good, the water is removed, and electrolyte is added through the large hole set in the top of the upper clamp. The electrolyte can be sodium hydroxide solution or sulfuric acid solution. Whether to add poisoning agents such as thiourea to the electrolyte and the concentration of the electrolyte are determined according to actual needs. Before the test begins, the punch is inserted through the holes in the lower clamp and the positioning cylindrical shell to make it contact the sample. A platinum electrode, acting as the positive electrode, is inserted through a small hole in the top of the upper clamp to make it contact the electrolyte. The negative electrode of the galvanometer is connected to the thin wall at the edge of the lower part of the punch's disc, and the positive electrode of the galvanometer is connected to the platinum electrode. The required current density and small punch test parameters are set, and the test can then begin to obtain the desired mechanical properties and other useful parameters. Extensive testing has verified that the data obtained using the device proposed in this invention for small punch testing in a hydrogen environment is reliable, the test time is short, and the device is easy to manufacture, install, store, and maintain, with simple operation and high safety. Attached Figure Description

[0007] Figure 1 This is a schematic diagram of a small punch test device for testing hydrogen-induced performance damage of materials in a hydrogen environment. Figure 2 This is a 3D modeling schematic diagram of a small punch test device for testing hydrogen-induced performance damage of materials in a hydrogen environment. Figure 3 This is a three-dimensional exploded view of a small punch test apparatus for testing hydrogen-induced performance damage of materials in a hydrogen environment. Figure 4 The test force-displacement curve is obtained by testing using the device proposed in this invention; In the figure: 1. Upper clamp; 11. Small hole; 12. Large hole; 13. First cavity; 14. Second cavity; 15. Third cavity; 2. Lower clamp; 3. Sealing ring; 4. Positioning cylindrical shell; 5. Punch rod; 6. Test sample; 7. Platinum electrode. Detailed Implementation

[0008] The invention will be further described below with reference to the accompanying drawings and experimental procedures.

[0009] like Figure 1 , Figure 2 and Figure 3 As shown, a small punch test apparatus for testing hydrogen-induced performance damage of materials under hydrogen environment includes: an upper clamp 1, a lower clamp 2, a positioning cylindrical shell 4, and a punch 5; the upper clamp 1 and the lower clamp 2 are fastened together, the positioning cylindrical shell 4 is disposed inside the upper clamp 1, and the punch 5 is disposed inside the positioning cylindrical shell 4; wherein: The upper clamp 1 includes an upper cylindrical shell and a lower cylindrical shell connected in series. The top of the upper cylindrical shell is closed, and a small hole 11 and a large hole 12 are provided on the top surface. The small hole 11 has a diameter of 3 mm and its center is 11 mm away from the central axis of the upper clamp. The small hole 11 accommodates a platinum sheet electrode 7. Electrolyte is filled inside the upper cylindrical shell, and the platinum sheet electrode extending into the small hole 11 is in complete contact with the electrolyte. The large hole 12 has a diameter of 6 mm and its center is 12.5 mm away from the central axis of the upper clamp. The large hole 12 is used for adding and pouring out the electrolyte stored in the first cavity 13, and facilitates... Observe the amount of added liquid, especially in the later stages of the test when the sample enters the failure stage. The electrolyte may flow down the wall of the punch rod. At this time, it is necessary to observe the rate of descent of the solution level through this large hole 12 to determine whether it is necessary to add electrolyte into the upper cylindrical shell. The outer surface of the lower cylindrical shell is provided with external threads. The upper clamp 1 includes, from top to bottom, a through first cavity 13, a second cavity 14, and a third cavity 15. The first cavity 13 has a diameter of 38 mm and a height of 17 mm and is cylindrical. The main function of the first cavity 13 is to store the added electrolyte. The first cavity 13 contains the electrolyte; the second cavity 14 has a diameter of 4 mm and a height of 6 mm, and is cylindrical. The diameter of the second cavity 14 should not be too small, otherwise it may not be able to fully contact the sample surface due to the surface tension of the liquid. The main function of the second cavity 14 is to guide the electrolyte in the first cavity 13 to the surface of the sample 6, so that the electrolyte and the sample 6 are in full contact. The part in full contact between the electrolyte and the sample 6 is the part that participates in the electrolysis reaction, that is, the electrochemical hydrogen charging region or the hydrogen permeation region; the main body of the third cavity 15 has a diameter of 4 mm and a height of 6 mm, and is cylindrical. The first cavity 13 has a diameter of 12mm and a height of 18.5mm. The top surface of the third cavity has a sample groove with a diameter of 10mm and a height of 0.5mm, and a sealing ring groove with an outer diameter of 8mm and an inner diameter of 6mm. The main body of the third cavity 15 is coaxially arranged with the sealing ring groove and the sample groove. The main function of the third cavity 15 is to facilitate the placement of the sealing ring 3, the test sample 6, and the positioning cylindrical shell 4. The third cavity 15 also guides the positioning cylindrical shell 4. External threads are provided on the outer periphery of the upper clamp 1 located at the third cavity 15 for threaded connection with the lower clamp 2. During the test, the upper clamp 1 experiences significant force, especially the components near the first cavity 13. Therefore, the wall thickness of the first cavity 13 should not be too small, ideally between 2mm and 6mm. Too small a wall thickness may lead to premature failure of the device and a shorter lifespan, while too large a wall thickness may result in insufficient electrolyte addition, incomplete contact between the solution and the sample surface, and difficulty in observing the solution level within the device.

[0010] The positioning cylindrical housing 4 is disposed within the third cavity 15 and is clearance-fitted with the upper clamp 1. A hole with a diameter of 2.5 mm and a height of 5 mm is provided at the top of the positioning cylindrical housing 4. This hole is used to insert the head of the punch 5, allowing the punch 5 to directly contact the sample. The end of the positioning cylindrical housing 4 that contacts the test sample 6 has an outer diameter of 10 mm and a height of 4.5 mm, while the remaining portion has an outer diameter of 12 mm and a height of 20 mm. The positioning cylindrical housing 4 contains... A 6mm diameter and 18mm height hole is used to guide the punch 5; the positioning cylindrical shell 4 protrudes from the upper clamp 1 after being inserted into the upper clamp 1, with a protrusion height of 5mm; the lower clamp 2 is a hollow shell adapted to the upper clamp 1, and the lower clamp 2 is provided with internal threads. The lower clamp 2 is threadedly connected to the upper clamp 1. After the upper clamp 1 and the lower clamp 2 are threadedly connected, force is applied to the test sample 6 through the lower clamp 2 and the positioning cylindrical shell 4, firmly fixing the test sample 6 in the sample slot; the positioning cylindrical shell A suitable cavity is provided inside the body 4 to accommodate the punch 5 and to allow the head of the punch 5 to contact the test sample. The third cavity 15 provided in the upper clamp 1 guides the positioning cylindrical shell 4, and the positioning cylindrical shell 4 also guides the punch 5. Holes are also provided on the lower clamp 2 to allow the punch 5 to enter. The head of the punch 5 is hemispherical with a diameter of 2.5 mm, and it directly contacts the test sample 6. A disk is provided at the lower part of the punch 5, and a thin wall is provided around the disk. The purpose is as follows: First, the negative electrode of the ammeter can be connected to the thin wall to conduct current, and the thin wall can be connected to the negative electrode of the ammeter. The current will be guided along the punch to the test sample 6. The positive electrode of the ammeter is connected to the platinum electrode 7. Second, the geometric characteristics of the disk allow the entire device to be placed stably on the test platform. Third, if the sample fails and cracks in the later stage of the test, a small amount of electrolyte may flow down along the punch wall. The geometric characteristics of the disk and the thin wall allow the electrolyte to be temporarily stored on the disk and prevent it from overflowing.

[0011] The lower clamp 2 includes a cylindrical shell at the top and a prismatic shell at the bottom. The outer diameter of the cylindrical shell at the top is 46 mm and the wall thickness is 10 mm. The prismatic shell at the bottom has a ridge height of 10 mm and a hexagonal side length of 17 cm. A through hole with a diameter of 6 mm is provided at the bottom end of the lower clamp 2. An internal thread is provided in the lower clamp 2, which mates with the external thread on the surface of the upper clamp 1. After tightening, the lower clamp 2 provides a clamping force to the positioning cylindrical shell 4. The lower clamp 2 and the positioning cylindrical shell 4 together fix the test sample 6 in the sample slot and ensure a seal. The through hole in the lower clamp 2 is for inserting the punch 5 to mate with the positioning cylindrical shell 4, so that the punch 5 can contact the sample surface.

[0012] The part of the punch rod 5 that contacts the sample is the punch area. The head of the punch area is a hemisphere with a diameter of 2.5 mm, and the rest is a cylinder with a diameter of 2.5 mm and a height of 9 mm. The middle area has a diameter of 3.5 mm-6 mm and a height of 39 mm. The bottom of the punch rod 5 is connected to a disk with a diameter of 30 mm and a height of 3 mm. A thin wall with a thickness of 3 mm and a height of 5 mm is set around the disk.

[0013] When testing the hydrogen-induced damage performance of the material using this invention, the punch 5 is in direct contact with the test sample 6, the positioning cylindrical shell 4, and the lower clamp 2. When energized, an electrolytic reaction also occurs inside the upper clamp 1 where it contacts the electrolyte, resulting in current loss. Therefore, in this invention, the upper clamp 1, lower clamp 2, and positioning cylindrical shell 4 are made of alumina ceramic material, the punch 5 is made of 304 stainless steel, and the sealing ring 3 can be a fluororubber O-ring. Alumina ceramic material has good mechanical properties, high impact resistance, excellent insulation properties, and certain corrosion resistance. Furthermore, alumina ceramic material is easy to process, making it an excellent material for manufacturing the device proposed in this invention.

[0014] The test method for the small punch test device for testing hydrogen-induced performance damage of materials under hydrogen environment is as follows: During use, place the sealing ring 3 into the sealing groove, then place the prepared test sample 6 into the sample groove, and place the positioning cylindrical shell 4 into the third cavity 15 of the upper clamp 1. After the positioning cylindrical shell 4 is placed, the lower clamp 2 and the upper clamp 1 are threaded together and tightened. The test sample 6 is fixed in the sample groove by the lower clamp 2 and the positioning cylindrical shell 4, ensuring close contact between the sample and the sealing ring 3 to guarantee good sealing performance. Then, pour water into the large hole 12 at the top of the upper clamp 1. Observe for 5 minutes through the holes provided by the lower clamp 2 and the positioning cylindrical shell 4 to check whether the device has good sealing performance. After the sealing performance check is completed, remove the water and continue to add an appropriate amount of prepared electrolyte solution through the large hole 12. The punch 5 is then installed and connected to the current meter. After setting the positive and negative electrodes, the entire device is moved onto the testing machine. A platinum electrode is inserted through the small hole 11 at the top of the upper clamp 1 and connected to the positive electrode of the galvanometer. The negative electrode of the galvanometer is connected to the thin wall at the bottom of the punch 5. At this time, a complete circuit is formed through the galvanometer, punch 5, test sample 6, electrolyte, and platinum electrode. Hydrogen is generated in the area where the test sample is in contact with the electrolyte. At the same time, the current intensity and testing machine parameters are set, the power is turned on, and the testing machine is turned on. The punch 5 begins to punch the test sample 6 upward with the displacement rate set by the testing machine. At the same time, the test force sensor at the top of the punch 5 records the top force of the punch 5 in real time, and the displacement sensor also records the displacement data of the punch 5 moving upward in real time. After the sample breaks and fails, the test force-displacement curve will drop rapidly, and the test ends. Then, the performance parameters of the sample under hydrogen environment can be obtained through relevant data processing.

[0015] like Figure 4 As shown in the figure, the curve is the test force-displacement curve obtained by the test device and method proposed in this invention. The test conditions are as follows: the test sample 6 is L360 pipeline steel, at room temperature and a displacement rate of 0.2 mm / min, under conditions of no hydrogen purging and 30 mA / cm 2 The experimental results obtained by charging with hydrogen at a current density clearly demonstrate the effectiveness and efficiency of the experimental apparatus proposed in this invention in assessing the degree of hydrogen-induced property damage to materials. Furthermore, the experimental data also exhibit high reliability and good repeatability.

[0016] The small punch test device for testing hydrogen-induced performance damage of materials under hydrogen environment proposed in this invention has an ingenious structural design, is simple to operate, and has high testing efficiency, safety, and reliability. It is easy to manufacture, install, and maintain, and can effectively and quickly assess the degree of hydrogen-induced performance damage of materials. With appropriate sampling methods, it can assess the degree of hydrogen-induced mechanical performance damage of in-service pipelines with minimal or near-non-destructive testing without interrupting gas flow or transportation. It can provide a practical testing method and theoretical basis for the construction of hydrogen-blended and pure hydrogen pipelines in my country.

Claims

1. A small punch test apparatus for testing hydrogen-induced property damage of materials under hydrogen environment, comprising: The device comprises an upper clamp, a lower clamp, a positioning cylindrical shell, and a punch; the upper and lower clamps are threadedly connected, the positioning cylindrical shell is disposed within the cavity of the upper clamp, and the punch is disposed within the positioning cylindrical shell; characterized in that: the upper clamp includes an upper cylindrical shell and a lower cylindrical shell connected in series, and the upper clamp includes, from top to bottom, a first cavity, a second cavity, and a third cavity; the upper cylindrical shell is equipped with an electrolyte and a platinum electrode, the top surface of the third cavity is provided with a sample groove and a sealing ring groove, the positioning cylindrical shell is disposed within the third cavity of the upper clamp and is clearance-fitted with the upper clamp, the positioning cylindrical shell protrudes from the upper clamp after being inserted into the upper clamp, and a disk is disposed at the lower part of the punch, with a thin wall disposed around the disk.

2. The small punch test apparatus for testing hydrogen-induced performance damage of materials under hydrogen environment according to claim 1, characterized in that, The top surface of the upper cylindrical shell is provided with small holes and large holes. The small holes accommodate platinum sheet electrodes, and the platinum sheet electrodes that extend into the small holes are in complete contact with the electrolyte.

3. The small punch test apparatus for testing hydrogen-induced performance damage of materials under hydrogen environment according to claim 1 or 2, characterized in that, The small hole has a diameter of 3mm and its center is 11mm away from the centerline of the clamp. The large hole has a diameter of 6mm and its center is 12.5mm away from the centerline of the clamp. The first cavity has a diameter of 38mm and a height of 17mm and is cylindrical. The second cavity has a diameter of 4mm and a height of 6mm and is cylindrical. The main body of the third cavity has a diameter of 12mm and a height of 18.5mm. The top surface of the third cavity is provided with a sample groove with a diameter of 10mm and a height of 0.5mm and a sealing ring groove with an outer diameter of 8mm and an inner diameter of 6mm. The main body of the third cavity, the sealing ring groove, and the sample groove are coaxially arranged.

4. The small punch test apparatus for testing hydrogen-induced performance damage of materials under hydrogen environment according to claim 3, characterized in that, The top of the positioning cylindrical housing has a hole with a diameter of 2.5 mm and a height of 5 mm. The outer diameter of the end of the positioning cylindrical housing that contacts the test sample is 10 mm and the height is 4.5 mm, while the outer diameter of the remaining part is 12 mm and the height is 20 mm. The positioning cylindrical housing has a hole with a diameter of 6 mm and a height of 18 mm inside for guiding the punch rod. After the positioning cylindrical housing is installed in the upper clamp, the part protruding from the upper clamp has a height of 5 mm.

5. The small punch test apparatus for testing hydrogen-induced property damage of materials under hydrogen environment according to claim 1 or 2, characterized in that, The lower clamp is a hollow shell that fits the upper clamp. The outer surface of the lower cylindrical shell in the upper clamp is provided with external threads, and the lower clamp is provided with internal threads. The lower clamp and the upper clamp are threaded together. The positioning cylindrical shell is provided with a cavity to accommodate the punch and make the head of the punch contact the sample to be tested. The head of the punch is hemispherical with a diameter of 2.5 mm, and it directly contacts the sample to be tested.

6. The small punch test apparatus for testing hydrogen-induced performance damage of materials under hydrogen environment according to claim 1 or 2, characterized in that, The lower clamp consists of a cylindrical shell at the top and a prismatic shell at the bottom. The cylindrical shell at the top has an outer diameter of 46 mm and a wall thickness of 10 mm. The prismatic shell at the bottom has a ridge height of 10 mm and a hexagonal base with a side length of 17 cm. A through hole with a diameter of 6 mm is provided at the bottom end of the lower clamp. An internal thread is provided inside the lower clamp, which mates with the external thread provided on the surface of the upper clamp.

7. The small punch test apparatus for testing hydrogen-induced performance damage of materials under hydrogen environment according to claim 1 or 2, characterized in that, The part of the punch that contacts the sample is the punch area. The punch is a hemisphere with a diameter of 2.5 mm, and the rest are cylinders with a diameter of 2.5 mm and a height of 9 mm. The size of the middle area is 3.5 mm-6 mm in diameter and 39 mm in height. The bottom end of the punch 5 is connected to a disk with a diameter of 30 mm and a height of 3 mm. A thin wall with a thickness of 3 mm and a height of 5 mm is set around the disk.

8. The test method of the small punch test apparatus for testing hydrogen-induced property damage of materials in a hydrogen environment as described in claims 1-7, characterized in that: During the test, the sealing ring is placed in the sealing groove, and the prepared test sample is placed in the sample groove. The positioning cylindrical shell is placed in the third cavity of the upper clamp. After the positioning cylindrical shell is placed, the lower clamp and the upper clamp are threaded together and tightened. The test sample is fixed in the sample groove by the lower clamp and the positioning cylindrical shell, ensuring that the sample is in close contact with the sealing ring and good sealing performance. Then, water is added through the large hole at the top of the upper clamp. The device is observed for 1 minute through the holes set in the lower clamp and the positioning cylindrical shell to check whether the device has good sealing performance. After the sealing performance is checked, the water is removed, and an appropriate amount of prepared electrolyte solution is added through the large hole. After the punch is installed and the positive and negative electrodes are connected, the entire device is moved onto the testing machine. A platinum electrode is placed in a small hole and connected to the positive terminal of a galvanometer. The negative terminal of the galvanometer is connected to the thin wall at the bottom of the punch. At this point, a complete circuit is formed through the galvanometer, the punch, the test sample, the electrolyte, and the platinum electrode. Hydrogen is generated in the area where the test sample is in contact with the electrolyte. The current intensity and testing machine parameters are set, the power is turned on, and the testing machine is started. The punch begins to thrust upwards at the test sample according to the displacement rate set by the testing machine. At the same time, the test force sensor at the top of the punch records the force at the top of the punch in real time, and the displacement sensor also records the displacement data of the punch moving upwards in real time. After the sample breaks and fails, the test force-displacement curve will drop rapidly, and the test ends. Then, the performance parameters of the sample under hydrogen environment are obtained through relevant data processing.

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